I don't use slathers anymore but if I did I would try it.
Salt the meat first, let it sit for a bit and it draws moisture to the surface which helps the rub stick.
Did this for the 1st time when I smoked a turkey breast for Thanksgiving. I must say that I was pleasantly surprised with the result. I actually got some crispy skin.
Only time I slather is low and slow for a binder, I've used mayo and see no advantage over cheap generick mustard other than its 3 times as expensive. I have found nothing makes a differance in flavor, except the seasonings I use one it.
